Lamella core and a method for producing it

ABSTRACT

The disclosure relates to a semi product for building panels or structural elements comprising several wood lamellas ( 5 ) fixed by distance elements ( 4 ), a building panel with such a semi product and a method of producing the semi product and the building panel.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of U.S. ProvisionalApplication No. 61/594,059, filed on Feb. 2, 2012. The entire contentsof U.S. Provisional Application No. 61/594,059 are hereby incorporatedherein by reference in their entirety.

TECHNICAL FIELD

The disclosure generally relates to the field of cores comprisingseveral wood lamellas and building panels, e.g. floor and wall panels,comprising such a core, a decorative surface layer and a balancing.Furthermore, the disclosure relates to production methods to producesuch cores and panels. Also disclosed is a structural element, such as abeam, comprising wood lamellas.

BACKGROUND

It is well known to produce building panels, e.g. floor panels,comprising a wood lamella core, see e.g. CA 430 631. It is also wellknown to produce building panels with a mechanical locking system, seee.g. WO 1994/026999.

An engineered wood floor generally comprises of a surface layer, a corelayer and a balancing layer. The core provides stability and counteractsswelling/shrinking. Several core materials may be used such as plywood,HDF boards or a lamella core comprising several wood lamellas.

SUMMARY OF THE INVENTION

An overall objective of the invention is to improve the yield of theproduction of a wood lamella core for building panels, particular panelscomprising a mechanical locking system. The mechanical locking systemmay be provided on long and/or short edges that may be locked withvarious combinations of angling and vertical or horizontal snapping. Aspecific objective is to improve the locking system, especially whensuch system is formed in a wood core.

The material used for wood lamella cores is due to cost reasons normallyof low grade with a high number of knots, cracks etc. Furthermore theincoming material is in different lengths and the lengths seldomcorrespond to the exact length needed in the production. This causes amaterial waste in the production of the wood lamella core. The inventionincreases the share of the incoming material that is possible to use inthe production of building panels with a wood lamella core.

A first aspect of the invention is a semi-product for a structuralelement, such as a beam, or for a core for a building panel. The semiproduct comprising several wood lamellas, which are arranged essentiallyparallel to each other and with long edge to long edge. A long edge of afirst wood lamella is fixed to a long edge of an adjacent second woodlamella by a fastening element, preferably an adhesive and/or a distanceelement. The long edge of the first wood lamella is preferably fixed byat least two fastening elements to the long edge of the adjacent secondwood lamella. The fastening elements secure the wood lamellas in thesemi-product, which makes it possible to use lower grade material withcracks or knots and/or with different lengths. This increases thesurface area of core material produced per incoming volume.

The semi product is easier to handle in the production than the separateand loose wood lamellas known in the art. The invention also makes iteasier to control the total length of the wood lamella core. The pieceof a semi product, which is cut away to adjust the total length of thesemi products to the length of a wood lamella core of a building panel,may be used in another wood lamella core.

The fastening elements furthermore assure a defined position between thewood lamellas. If the position of the wood lamellas is not fixed and thewood lamellas can be displaced easily and randomly in the process, as isthe case with known technology, the result may be a few large openings,which causes a downgrading and/or may require a manual correction oflarge gaps.

In the production of a wood lamella building panel, with a mechanicallocking system at long and short edge, normally the wood lamella corehas to be replaced at the short edges with a short edge core material,which is more homogeneous, stronger and consequently more expensive thanthe wood lamella core. The invention makes it easier to control thetotal length of the wood lamella core, thus enabling the use of asmaller piece for the short edge material.

The fastening element may be an adhesive which may be e.g. a bridgeadhesive, a building adhesive, an expanding adhesive or a self-foamingglue such as PU-adhesive. The adhesive may be a hot melt adhesiveapplied with a foaming unit.

The distance elements may comprise wood fibres and said distanceelements may be fixed to the first wood lamella and the adjacent secondwood lamella by an adhesive, such as resins, preferably cross-linked,hot melt glue, white glue or glue comprising polyvinyl acetate orpolyurethane. The distance elements may alternatively comprise veneer,recycled parts of wood lamellas, paper, MDF, HDF, OSB, saw dust mixedwith resin, or resin with a filler.

The distance between the long edge of the first wood lamella and thelong edge of the adjacent second wood lamella in the core for thebuilding panel may be in the range of about 0.5 mm to about 15 mm,preferably in the range of about 1 mm to about 5 mm generally dependingamong other things on the thickness of the surface layer that mustoverbridge the distance between the wood lamellas.

The first or the second wood lamella may comprise in its lengthdirection two pieces spaced from each other by a space at short edges ofsaid pieces, since the distance element secures the pieces in the semiproduct.

The space may be arranged at one of the distance elements, in order tomakes the semi-product even stronger.

An enforcement element may be arranged at the space or at a knot orother weakness of a wood lamella, in order to further increase thestrength of the semi-product.

A part of the distance element may be positioned in a groove in thefirst wood lamella.

Another part of the distance element may be positioned in another groovein the second wood lamella.

A third wood lamella may be fixed to a second wood lamella by a seconddistance element, a fourth wood lamella may be fixed to the third woodlamella by a third distance element, wherein the distance element, thesecond distance element and the third distance element are preferablyarranged in a straight line.

The straight line may be oriented at about 45 degrees to thelongitudinal direction of the first wood lamella.

The outer long edge of the outermost wood lamella may be provided withdistance elements. If several semi products are arranged next to each inthe production of a building panel the distance between adjacentsemi-products is secured.

The cavity between two adjacent wood lamellas may be filled with soundreducing material or insulating material.

A second aspect of the invention is a method of producing asemi-product, preferably the semi-product for a core for a buildingpanel according to the first aspect, wherein the method comprises thesteps of:

-   -   applying a fastening element, preferably at least two distance        strips, at a distance essentially equal to the width of the        ready building panel, and an adhesive, the strips are preferably        arranged essentially perpendicular to the first wood board;    -   attaching a second wood board to said first wood board by said        fastening element, preferably by applying an adhesive, and        thereby obtaining a batch comprising the first and the second        wood board and the distance strip; and    -   cutting said batch in the length direction of the wood boards,        preferably by a multi rip saw, a frame saw or a band saw.

The method may comprise the step of adding further wood boards andfastening elements, preferably distance strips, to said batch byattaching several wood boards to the second and/or the first wood boardand preferably at least two distance strips between adjacent woodboards.

A preferred batch comprises at least three wood boards and the cuttingis made by a band saw or a frame saw.

The method may comprise the step of arranging the distance stripsbetween adjacent wood boards in a straight line.

The straight line may be oriented at about 90 degrees to thelongitudinal direction of the first wood board.

The method may also be used to produce a semi-product for a structuralelement, preferably according to the sixth aspect, such as a beam,wherein the straight line is preferably oriented at about 45 degrees tothe longitudinal direction of the first wood board.

The method may comprise the step of cutting the first and the secondwood boards and the distance strips in a direction perpendicular to thelength direction.

If the wood boards are cup shaped the method preferably comprises thesteps of:

-   -   forming two grooves, preferably with essentially planar fixation        surfaces, in a surface of the first wood board; and    -   attaching one of said two distance strips in each groove.

If the wood boards are cup shaped the method preferably also comprisesthe steps of:

-   -   forming two grooves, preferably with essentially planar fixation        surfaces, in a surface of the second wood board; and    -   attaching one of said two distance strips in each of said        grooves in the surface of the second wood board.

By forming grooves in the first and the second wood boards planarsurfaces are provided for attaching the strips. This has the effect thatthe fixation strength between the strips and the wood boards areincreased.

The method may comprise the step of cutting the first and the secondwood board and the distance strips in the length direction several timeswith a distance between the cuts which is equal to the thickness of thea semi-product.

A third aspect of the invention is a building panel comprising a woodlamella core comprising the semi product according to the first aspect,a decorative surface layer on top of the core and balancing layer underthe core. The building panel may be provided with a mechanical lockingsystem along its long edges and the distance elements are preferablyarranged at the long edges at the mechanical locking system. This makesthe locking system stronger and delimits the risk for tearing out parts,splinters or chips of the wood lamellas at the edge, especially at thelocking element, during the profiling operation. Tearing out parts,splinters or chips of the wood lamellas at the edge is negative for thestrength of the mechanical locking system and for the qualityimpression. The openings at the edge, if not closed by the distanceelements, may also carry a lot of splinters and dust from the profilingoperation. Later, this can cause indentation marks when the ready boardsare packed.

A forth aspect of the invention is a building panel, such as afloorboard, comprising a wood lamella core, a decorative surface layeron top of the core and balancing layer under the core. The corecomprises several wood lamellas, which are arranged essentially parallelto each other and with long edge to long edge. A long edge of a firstwood lamella is arranged with a distance to a long edge of an adjacentsecond wood lamella. The long edge of the first wood lamella is fixed bya distance element to the long edge of the adjacent second wood lamellaand at a first edge of the building panel. A first mechanical lockingdevice is formed at the first edge of the building panel and at leastpartly in the distance elements. This makes the first mechanical lockingsystem stronger and delimits the risk for tearing out parts, splintersor chips of the wood lamellas at the edge when the first mechanicallocking device is formed, preferably by milling. Tearing out parts,splinters or chips of the wood lamellas at the edge is negative for thestrength of the first mechanical locking device and for the qualityimpression. The openings at the edge, if not closed by the distanceelements, may also carry a lot of splinters and dust from the profilingoperation. Later, this can cause indentation marks when the readybuilding panels are packed.

Preferably, the long edge of the first wood lamella is fixed by a seconddistance element to the long edge of the adjacent second wood lamellaand at a second opposite edge of the building panel, wherein thedistance element and the second distance element are arranged at adistance, preferably with a cavity in between.

A part of the distance element may be positioned in a first groove inthe first wood lamella, and a part of the second distance element ispositioned in a second groove in the first wood lamella in order toimprove the fixation to the first wood lamella.

Preferably another part of the distance element and the second distanceelement are positioned in a third and a fourth groove, respectively, inthe second wood lamella.

A second mechanical locking device may be formed at the second oppositeedge of the building panel and at least partly in the second distanceelements.

The distance element may extends to a second opposite edge of thebuilding panel, wherein a second mechanical locking device may be formedat the second opposite edge of the building panel and at least partly inthe distance elements.

The first mechanical locking device may be configured to cooperate withthe second mechanical locking device at an essential identical buildingpanel for vertical and/or horizontal locking of the building panel andthe essential identical building panel.

The second locking device may comprise a locking groove at the secondopposite edge of the groove panel.

The first locking device may comprise a protruding strip with a lockingelement. The protruding strip is enforced by the distance elementbetween the wood lamellas.

The locking element and the locking groove are configured to cooperatefor the locking in the horizontal direction.

The first or the second locking device may comprises a tongue and theother of the first or the second locking device may comprises a tonguegroove, wherein the tongue and the tongue groove are configured tocooperate for the locking in the vertical direction.

The distance element may be of a different material or of differentproperties, e.g. different wood species and/or wood with different woodfibre directions, than the wood lamellas.

The wood lamella core preferably comprises several semi productsaccording to the first aspect.

A fifth aspect of the invention is a method for producing a buildingpanel according to the third aspect. The method comprising the steps of:

-   -   arranging several semi-products next to each other, with an        outer wood lamella of each semi product adjacent an outer wood        lamella of an adjacent semi-product;    -   positioning the balancing layer on a first side of the        semi-products, preferably essentially perpendicular to the        longitudinal direction of the wood lamellas of the        semi-products;    -   arranging the decorative layer on a second side of the        semi-products, preferably essentially perpendicular to the        longitudinal direction of the wood lamellas of the        semi-products; and    -   cross cutting the semi-products along an edge of the decorative        layer, preferably at the distance elements and even more        preferably through the distance elements.

The method may comprise the step of producing a mechanical lockingsystem along the long edges of the decorative layer in the wood lamellacore.

The method may comprise the step of arranging a core material ofdifferent material, e.g. a piece of plywood at a short edge of thedecorative layer, and preferably producing a mechanical locking systemalong the short edge of the decorative layer and in the core material ofdifferent material.

The method may comprise the step of arranging a distance element betweentwo adjacent semi-products between the outer most wood lamellas of saidtwo adjacent semi-products.

The method may also be used to produce the building panel according tothe forth aspect, wherein the locking system comprises the first lockingdevice along a first long edge and the second locking device along asecond long edge.

A sixth aspect of the invention is a structural element, such as a beam,comprising a web of wood lamellas. The web comprises a first layercomprising wood lamellas and a second layer comprising wood lamellas.The first layer is arranged such that the length direction of at leastsome of the wood lamellas is oriented essentially perpendicular to thelength direction of at least some of the wood lamellas in the secondlayer.

Preferably, essentially all wood lamellas in the first layer arearranged perpendicular to essentially all wood lamellas in second layer.

By arranging the first and the second layer such that the wood lamellasin the first layer are essentially perpendicular to the wood lamella inthe second layer the strength of the structural element is increased.

To minimize the weight of the structural element the width of thedistance element are preferably wider than the width of the woodlamellas.

A first wood lamella in the first layer may be fixed to a second woodlamella in the first layer by a distance element.

A first wood lamella in the second layer may be fixed to a second woodlamella in the second layer by a distance element.

The first layer may be fixed to the second layer, preferably by gluingat some of the distance elements and/or at a crossing of the first andthe second layer.

A preferred embodiment is a beam comprising a first flange, attached toends of the wood lamellas in the first and a second layer, and a secondflange, attached to opposite end of the wood lamellas.

The beam may have some wood lamellas, which are arranged perpendicularto the first and the second flange, preferably at the longitudinal endsof the beam.

A seventh aspect of the invention is a set of rectangular building panelwith a surface layer, a core and a long edge locking system. The lockingsystem comprising a tongue and a groove for vertical locking of adjacentedges and a protruding strip with a locking element at a first edge thatcooperates with a locking groove at a second adjacent edge forhorizontal locking of the adjacent edges. The protruding strip comprisesseveral sections along the joint. Said sections have different widths inthe length direction of the joint and/or different material properties,e.g. different wood species and/or wood with different wood fibredirections.

The rectangular building panel may comprise a wood lamella core withlamellas that are spaced from each other in an inner part of the core.

An eighth aspect of the invention is a building panel with a surfacelayer and a multi-layer wood lamella core wherein the core consists oftwo sets of wood lamellas, an upper set attached to the surface layerand a lower set attached to the upper set, wherein each set compriseswood lamellas spaced from each other in a main plane of the panel.

The average distance between the lamellas in the lower set may be largerthan the average distance between the lamellas in the upper set.

The building panel may comprise lamellas that are attached to each otherwith distances.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will in the following be described in connection topreferred embodiments and in greater detail with reference to theappended exemplary drawings, wherein:

FIGS. 1 a-c show the production of a wood lamella core according toknown technology.

FIGS. 1 d-e illustrate a wood board and a batch comprising several woodboards and distance strips according to an embodiment of the invention.

FIG. 2 illustrates a batch comprising several wood boards according toan embodiment of the invention.

FIGS. 3 a-3 b illustrate a semi product according to an embodiment ofthe invention.

FIGS. 3 c-d illustrate a building panel according to an embodiment ofthe invention

FIGS. 4 a-4 b illustrate several semi product adjacent each other and abuilding panel respectively according to an embodiments of theinvention.

FIG. 5 illustrate a method of bonding wood boards and distance stripstogether according to an embodiment of the invention.

FIGS. 6 a-c illustrate a locking system with a protruding stripcomprising different sections according to an embodiment of theinvention.

FIGS. 7 a-f illustrate a multi-layer wood lamella core according to anembodiment of the invention.

FIGS. 8 a-d illustrate a balancing layer and a core comprising spacedapart sections according to embodiments of the invention.

FIGS. 9 a-d illustrate a batch and a wood board with a groove and abatch comprising such wood boards according to embodiments of theinvention.

FIGS. 10 a-b illustrate a batch of wood boards and distance strips and asemi product according to embodiments of the invention.

FIGS. 11 a-b illustrates semi products and a beam according toembodiments of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

In the production of a building panel, e.g. a floor panel, with a woodlamella core it is known to arrange wood lamellas 4 parallel to eachother and with a small distance between the wood lamellas as is shown inFIG. 1 a. The distance is undefined and random. A surface layer 6 isapplied and glued to the wood lamellas 4. The fibres in the wood lamellacore are generally oriented perpendicular to the fibre direction of thesurface layer 6. This provides a very climate stable floor panel whenthe surface layer is glued to the lamella core.

Generally the wood lamellas 4 have a length, which is equal to the widthof two or several floor panels as is shown in FIG. 1 b. The woodlamellas 4 are, after gluing of the surface layer 6, crosscut along along edge of a surface layer to obtain the building panel, see FIG. 1 c.

A batch according to an embodiment of the invention comprising woodboards 15 and distance strips 14 are shown in FIG. 1 e. The wood boards15 may be piled vertically above each other, with a distance strip 14,preferably of wood, between adjacent wood boards, as shown in FIGS. 1 aand 1 b, or arranged in the same way in the horizontal direction. Thedistance strips 14, between, a first 15 a and a second 15 b, and, asecond and a third 15 c, adjacent wood boards, are preferably arrangedvertically aligned. The wood species of the wood boards and/or thedistance strips may be, e.g., spruce, pine rubber wood or poplar.

The wood boards are preferably arranged such that the annual rings areoriented in the same way, see FIG. 1 e, and not opposite to each other,see FIG. 2. Different orientation of the annuals rings may cause thewood boards in the batch to crack and/or separate since the wood boardsare cupping, due to humidity changes, in different direction. Thecupping may be decreased by having narrower wood boards. The wood boardsare preferably divided into a width, which correspond to a multiple ofthe thickness of desired wood lamellas plus the width of any saw cut(s)between the wood lamella layers.

The batch may be used for producing a semi product, see FIGS. 3 a and 3b. The semi product may be used in a lamella wood core intended of abuilding panel, see FIGS. 3 c and 4 b.

Each distance strip 14 is fixed to the adjacent(s) wood boards 15 by anadhesive, e.g., such as resins, preferably cross-linked, hot melt glue,white glue, glue comprising polyvinyl acetate or polyurethane orexpanding/foaming glue. The longitudinal direction Z of the distancestrips 14 is preferably perpendicular to the longitudinal direction X ofthe wood boards 15.

The wood boards are divided several times by cutting in its longitudinaldirection X, forming a wood lamella 5, 5′, 5″ of the semi product, asshown in FIG. 3 a, and the distance strip is in the same cutting crosscut, forming a distance element 4, 4′ of the semi product.

The distance t between two adjacent cuts corresponds essentially to thethickness of the semi-product and thickness of the wood lamellas. Thedistance L1, in the longitudinal direction of the wood lamellas X,between two adjacent distance elements 4, corresponds preferably to thewidth of a ready-made building panel, see FIG. 3 a. The total length Lof the semi-product, in the longitudinal direction of the wood lamellasX, is preferably essentially equal to a multiple of the width, includingany mechanical locking system, of a ready-made building panel.

Knots 10 or other weaknesses 11 of the wood lamellas in the semi productare preferably enforced with an enforcement element 9, if they are notpositioned at a distance element 4. The wood lamella may comprise twopieces of wood in the longitudinal direction. The short edges of twoadjacent pieces may be close to each other 3 or positioned at somedistance 2. The short edges close to each other may be glued to eachother and the short edges positioned at some distance may be providedwith an enforcement element 9. The short edges of said two adjacentpieces may also be positioned at a distance element 4. The wood lamellasare preferably arranged such that short edges of a first wood lamella,with short edges between a pair of adjacent distance element, is notpositioned next to a second wood lamella with short edges positioned inthe longitudinal direction X between said pair of distance element ofthe second wood lamella.

A wood lamella 5′ at the outer edge of the semi product may be providedwith a distance element 4′. The purpose with this distance element 4′ isto position a first semi product at the desired distance from a secondsemi product when the first and the second semi product is arranged nextto each other, see FIGS. 3 a and 4 a.

FIGS. 3 c and 3 d disclose a building panel, preferably a floor panel,with a core comprising the semi products described above (section L1 inFIG. 3 a). The building panel is shown from above FIG. 3 c and in a sideview 3 d. The building panel further comprises a surface layer 6,preferably comprising wood or a wood veneer, and a balancing layer 8.Optionally the building panel may comprise a supporting layer 7, e.g. athin board or a veneer, in order to avoid telegraphing in top surface ofthe decorative layer 6. At the same time the thickness of surface layer6 can be reduced.

FIG. 4 a discloses several semi-products arranged in a set long side tolong side to be used as an element for the production of buildingpanels, see FIG. 4 b. In the production of building panels severaldecorative layers 6 may be positioned on one side of said set,preferably with their longitudinal direction perpendicular to thelongitudinal direction of the wood lamellas 5 of the semi products. Thelength of the set, in a direction Y perpendicular to the longitudinaldirection of the wood lamellas 5 in the semi products, is preferablyabout the same as the length of a ready-made building panel.

A long edge 45 of a decorative layer 6 may be arranged along a line 1 ofdistance elements 4. A balancing layer 8 may be arranged on the otherside of the set at each position of a decorative layer 6. The set ispreferably cut along said line 1 and a mechanical locking system formedalong the long edges of the building panel.

A core material of different material 44, e.g. a piece of plywood, maybe positioned in the set at a position, which corresponds to a shortedge 46 of the decorative layer. Different material 44 may be positionedat both short edges 46 of the decorative layer. Preferably a mechanicallocking system is produced along the short edges of the decorative layerand in the core material of different material. A core material ofdifferent material 44, e.g. a piece of plywood, may also be positionedin the set at a position that is essentially in the middle of thedecorative layer, or at any position where it may be desired to crosscutthe building panel and provide the edge with a mechanical lockingsystem.

FIG. 5 shows an embodiment of arranging and fixing the wood boards 15and the distance strips 14 to each other to obtain an endless batch. Thewood boards 15 are continuously fed between several guiding means 50positioned above each other. The wood boards are shown arranged aboveeach other in a pile, but may also be arranged next to each other in ahorizontal direction. The ends of the wood boards are positioned, in thelongitudinal direction of the wood boards, in the batch at irregularpositions, i.e. the ends are not arranged aligned. Distance strips 14are positioned between the wood boards 15 and an adhesive, preferably aglue, such as resins, preferably cross-linked, hot melt glue, white glueor glue comprising polyvinyl acetate or polyurethane, is applied, andthe wood boards are gradually pressed together by pressing devices 51.Wood boards 15, pre-cut to the same length, may also be used to create abatch with essentially the same length as the pre-cut wood boards.

Enforcement strips or elements may also be positioned at knots, weaknessor between short edges of two adjacent wood boards that are fed aftereach other. A vision system, comprising e.g. a camera and a computer,may be used to position the enforcement strips and elements at thecorrect position.

FIG. 6 a-c show a building panel comprising a wood lamella core and asurface layer 6. A first wood lamella 5 is fixed to a second adjacentwood lamella by a distance element 4. The building panel is providedwith a long edge locking system. The locking system comprises a firstlocking device at a first long edge and a second locking device at asecond opposite long edge. The first locking device comprises a groove62 and a protruding strip 60 with a locking element 63 at a first longedge. The second locking device comprises a locking groove 64 and tongue61.

The first locking device is configured to cooperate with the secondlocking device at an essentially identical adjacent building panel. Thetongue 61 and the groove 62 cooperate for vertical locking of the firstand the second edge of said two essentially identical building panels.The locking element 63 and the locking groove 64 cooperate forhorizontal locking of the first and the second edge of said twoessentially identical building panels.

The distance element 4 at the first edge preferably extends to an innerposition 4 a such that it covers the essentially whole groove 62. Theadvantage is that there is no open space 70 at the edge and between thewood lamellas 5, see FIG. 6 b, for accumulation of dust and splinters.Preferably the distance element 4 extends to an outer position at theouter edge of the locking element. This gives a strong locking and amore smooth machining since splitting of the locking element 63 at theouter edge of the wood lamella may be avoided, since the adjacent woodlamellas 5 are glued to the distance element 4 as shown in FIG. 6 c.

The distance element 4 at the first edge may also extend to an outerposition 4 b such that only a part of the strip 60 is covered. Thedistance element 4 may also extend to an inner position such that anopening is created between adjacent wood lamellas.

The locking system is made even stronger vertically if the distanceelement 4 at the second edge extends to the outer end of the tongue andto an inner position 4 c such that the distance element 4 covers thewhole tongue 61. The horizontal strength is improved if the distanceelement at the second edge extends to an inner position 4 d, such thatthe distance element covers a part of the locking groove 64, thatcooperates with the locking element 63 for horizontal locking.

The distance element 4 at the second edge may also extend to an innerposition 4 e, such that the distance element covers essentially thewhole locking groove 64, in order to avoid accumulation of dust andsplinters.

A preferred locking system of the building panel comprises a lockingstrip 60, which comprises a first section, with a first wood fibredirection, and a second section with a second wood fibre direction. Inthe embodiments shown in FIG. 6 a-c the first section is created by awood lamella and the second section is created by the distance element.

A locking system of the building panel may further comprise a protrudingstrip 60 that comprises sections with different materials and/or widthsalong the joint.

FIGS. 7 a-7 c show that further cost savings may be reached by forming acore comprising wood lamellas 5 a, 5 b with different widths and/ordistance elements 4 f, 4 g with different width. The core comprises twosets of wood lamellas, an upper and a lower set. The average width ofthe distance elements 4 g between the wood lamellas 5 a in the lower setmay be larger than the average width of the distance elements 4 fbetween the wood lamellas 5 b in the upper set. The average width of thewood lamellas 5 b in the lower set may be smaller than the average widthof the wood lamellas 5 a in the upper set. A layer may be appliedbetween the upper and the lower set, which is sound absorbing orthermally insulating.

It is possible to use more than two sets of wood lamellas and differentmaterials may be used in the upper and lower wood lamellas and also inthe same wood lamella set.

Such a multi-layer wood lamella core may provide considerable materialsavings. The weight of the panels may be reduced and this reduces thetransport costs and makes installation easier, especially when thepanels are of considerable length.

The space between the wood lamellas may be filled with different typesof materials, preferably with materials that have a lower density thanthe wood material. This may be used to reduce sound and/or to change thesound frequency. The spaces between wood lamellas may also be used toinclude materials that have a better heat transmission than woodmaterial to obtain an improved floor heating.

FIG. 8 a shows that cost savings may also be reached by modifying thebalancing layer 8 on the rear side of a panel. The balancing layer inknown multi-layer floor panels is generally a wood veneer that coversthe whole rear side. It is according to the invention possible to glueseveral veneer strips 65 to the wood lamellas 5 with a distance 66between the veneer strips 65. The precise positioning of the woodlamellas makes it possible to position the strips 65 such that theypreferably always cover all spaces between the wood lamellas. Thedistance between the veneer strips may be increased if for example thewood lamellas that cover a space between adjacent veneer strips arepreferably produced with a larger width than other wood lamellas. Thismeans that the wood lamellas in the core may have different widths.

FIG. 8 b show two panels that have been created by cutting the woodlamella core e.g. by sawing.

The method to form a balancing layer with separated materials,preferably with veneer strips as described above, may be combined withall other described embodiments.

The method to save material with several backing strips may also be usedin panels with a conventional wood lamella core or in panels with a corecomprising sheet material such as for example HDF, MDF or plywood.

The multi-layer core described above may also be used in panels wherethe core comprises HDF/MDF or plywood lamellas.

FIG. 8 c shows a side view of a building panel, preferably a wood basedfloor panel, comprising a surface layer 6, a balancing layer 8 and acore that is formed by several layers of wood veneer strips 80 a, 80 b,and 80 c connected to each other, preferably with glue. The veneerstrips are spaced from each other. Distance elements are not needed inthis embodiment, since a veneer may be cut with knives into veneerstrips with well-defined widths which are positioned and glued side byside with intermediate well defined distances and in at least two layersone over the other. The fibre direction may be the same in all corelayers. Distance elements may be used at edge portions of the finalpanel. This embodiment offers the advantages that no waste is caused bythe knife cutting and that a large portion of the wood veneers may beused when a large veneer sheet is cut into smaller strips. Cost savingsof more than 25% may be reached compared to for example a solid plywoodcore.

The wood veneer strips may be partly or completely replaced by stripsformed from a sheet material for example HDF/MDF. Thin HDF is ratherexpensive. It is therefore preferred to use a thicker board that may besliced into thinner material.

A preferred embodiment is a floor panel with a surface layer 6 with athickness of about 1-3 mm, at least three layers of veneer strips (80 a,80 b, 80 c) with a thickness of about 1-3 mm and a width of about 20-30mm, and a balancing layer with thickness of about 1-3 mm.

FIG. 8 d shows a locking system formed in a core comprising three layersof veneer strips as shown in FIG. 8 c. The locking strip 60 ispreferably formed in the lower 80 c and the middle layer 80 b. Thelocking element 63 and the locking groove 64 are preferably formed inthe same layer, preferably the middle layer 80 b, to obtain a strongerlocking.

FIG. 9 a shows a batch comprising cup shaped wood boards 15 and straightwood boards. The fixation strength between a distance strip 14 and a cupshaped wood boards is reduced since the distance 91, 92 between twoadjacent wood boards varies over the width of the adjacent wood boards.The distance variation may also result in that the wood boards crackwhen the wood boards in the batch are pressed together after that glueis applied between the distance strips and the wood boards. To improvethe fixation strength to a cup shaped wood board a groove 93, with aplanar fixation surface, is formed in the surface of the wood board 15,as is shown in FIGS. 9 b,c. The distance strip 14 is attached in thegroove, preferably by gluing the distance strip to the fixation surface.FIG. 9 d shows a batch with straight and cup shaped wood boards 15,which are provided with grooves 93 and distance strips 14 glued to thefixation surfaces of the grooves.

FIG. 10 a shows a batch comprising piled wood boards 15 and distancestrips 14 arranged between adjacent wood boards. The distance strips 14between the wood boards are arranged in straight lines 100. The straightlines are oriented at an angle of about 45 degrees to the longitudinaldirection of the wood boards. Each strip is glued to the adjacent woodboards.

A semi product 101 for a structural element, such as a beam, may beproduced by dividing the batch along the longitudinal direction of thewood boards and cutting along the straight line 100. Two such semiproducts are shown in FIG. 10 b. The wood boards are divided into woodlamellas 5 and the distance strips into distance elements 4. By turningone of the semi products, such that the lamellas of the two semiproducts are oriented perpendicular to each other and arranging them oneach other, see FIG. 11 a, a web for a structural element, such as abeam may be obtained, comprising a first layer comprising one of the twosemi-products and a second layer comprising the other of the two semiproducts.

FIG. 11 b shows a beam with a web comprising two semi products 101. Theweb comprises a first layer 101 comprising wood lamellas 5 and a secondlayer 102 comprising wood lamellas 5. The first layer is arranged suchthat the length direction of the wood lamellas is oriented essentiallyperpendicular to the length direction of the wood lamellas in the secondlayer.

A first wood lamella 5 in the first layer 101 is fixed to a second woodlamella in the first layer by a distance element 4.

A first wood lamella 5 in the second layer is fixed to a second woodlamella in the second layer 101 by a distance element 4.

The width of the distance element 4 may be larger than the width of thefirst wood lamella 5 and/or the width of the second wood lamella (notshown).

The first layer may be fixed to the second layer, preferably by gluingat some of the distance elements and/or at a crossing of lamellas of thefirst and the second layer. A first flange 111 is attached to ends ofthe wood lamellas in the first and a second layer, and a second flange111 is attached to opposite end of the wood lamellas.

The web may comprise some wood lamellas which are oriented essentiallyperpendicular to the first and the second flange (not shown).

Embodiments

1. Building panel, such as a floorboard, comprising a wood lamella core,a decorative surface layer on top of the core and balancing layer underthe core, the core comprises several wood lamellas, which are arrangedessentially parallel to each other and with long edge to long edge, anda long edge of a first wood lamella is arranged with a distance to along edge of an adjacent second wood lamella,

-   -   wherein the long edge of the first wood lamella is fixed by a        distance element to the long edge of the adjacent second wood        lamella and at a first edge of the building panel,    -   wherein a first mechanical locking device is formed at the first        edge of the building panel and at least partly in the distance        element.

2. The building panel as recited in embodiment 1, wherein the long edgeof the first wood lamella is fixed by a second distance element to thelong edge of the adjacent second wood lamella and at a second oppositeedge of the building panel, wherein the distance element and the seconddistance element are arranged at a distance, preferably with a cavity inbetween.

3. The building panel as recited in embodiment 2, wherein a part of thedistance element is positioned in a first groove in the first woodlamella, and a part of the second distance element is positioned in asecond groove in the first wood lamella.

4. The building panel as recited in embodiment 3, wherein another partof the distance element and the second distance element are positionedin a third and a fourth groove, respectively, in the second woodlamella.

5. The building panel as recited in any one of embodiments 2-4, whereina second mechanical locking device is formed at the second opposite edgeof the building panel and at least partly in the second distanceelement.

6. The building panel as recited in embodiment 1, wherein the distanceelement extends to a second opposite edge of the building panel, whereina second mechanical locking device is formed at the second opposite edgeof the building panel and at least partly in the distance element.

7. The building panel as recited in embodiment 5 or 6, wherein the firstmechanical locking device is configured to cooperate with the secondmechanical locking device at an essentially identical building panel forvertical and/or horizontal locking of the building panel and theessentially identical building panel.

8. The building panel as recited in any one of the embodiments 5-6,wherein the second mechanical locking device comprises a locking grooveat the second opposite edge of a groove panel.

9. The building panel as recited in any one of the precedingembodiments, wherein the first locking device comprises a protrudingstrip with a locking element.

10. The building panel as recited in embodiment 7, wherein the firstlocking device comprises a protruding strip with a locking element andthe second locking device comprises a locking groove at the secondadjacent edge, wherein the locking element and the locking groove areconfigured to cooperate for the locking in the horizontal direction.

11. The building panel as recited in embodiment 10 or 7, wherein one ofthe first or the second locking device comprises a tongue and the otherof the first or the second locking device comprises a tongue groove,wherein the tongue and the tongue groove are configured to cooperate forthe locking in the vertical direction.

12. The building panel as recited in any one of the precedingembodiments, wherein the distance element is of a different material orof different properties, e.g. different wood species and/or wood withdifferent wood fibre directions, than the wood lamellas.

13. A semi-product for a structural element or for a core for a buildingpanel, the semi product comprising several wood lamellas, which arearranged essentially parallel to each other and with long edge to longedge, a long edge of a first wood lamella is arranged with a distance toa long edge of an adjacent second wood lamella, and the long edge of thefirst wood lamella is fixed by a distance element, preferably at leasttwo distance elements, to the long edge of the adjacent second woodlamella.

14. The semi-product according to embodiment 13, wherein the distanceelements comprises wood fibres and is fixed to the first wood lamellaand the adjacent second wood lamella by an adhesive, such as resins,preferably cross-linked, hot melt glue, white glue or glue comprisingpolyvinyl acetate or polyurethane.

15. The semi-product as recited in embodiment 13, wherein the distancebetween the long edge of the first wood lamella and the long edge of theadjacent second wood lamella in the core for the building panel is inthe range of about 0.5 mm to about 15 mm, preferably in the range ofabout 1 mm to about 5 mm.

16. The semi-product as recited in any one of the embodiments 13-15,wherein the first or the second wood lamella comprises, in its lengthdirection, two pieces spaced from each other by a space at short edgesof said pieces.

17. The semi-product as recited in any one of the embodiments 13-16,wherein the distance element is positioned at a short edge of the firstand the second wood lamella.

18. The semi-product as recited in any one of the embodiments 13-17,wherein an enforcement element is arranged at the space or at a knot orother weakness of the wood lamella.

19. The semi-product as recited in any one of the embodiments 13-18,wherein an outer long edge of the outermost wood lamella is providedwith distance elements.

20. The semi-product as recited in any of the embodiments 13-19, whereina part of the distance element is positioned in a groove in the firstwood lamella.

21. The semi-product as recited in any of the embodiments 13-20, whereinanother part of the distance element is positioned in another groove inthe second wood lamella.

22. The semi-product as recited in any of the embodiments 13-21, whereina third wood lamella is fixed to second wood lamella by a seconddistance element, a fourth wood lamella is fixed to the third woodlamella by a third distance element, wherein the distance element, thesecond distance element and the third distance element are arranged in astraight line.

23. The semi-product as recited in embodiment 22, wherein the straightline is oriented at about 45 degrees to the longitudinal direction ofthe first wood lamella.

24. Method of producing a semi-product for a structural element,preferably according to any one of the embodiments 31-36, or for a corefor a building panel according to any one of the embodiments 13-23,wherein the method comprises the step of:

-   -   attaching at least two distance strips, preferably with a        distance essentially equal to the width of the building panel,        by an adhesive to a first wood board, the strips are preferably        arranged essentially perpendicular to the first wood board;    -   attaching a second wood board to the distance strips by an        adhesive; and    -   cutting the first and the second wood boards and the distance        strips in the length direction of the wood boards, preferably by        a multi rip saw, a frame saw or a band saw.

25. The method as recited in embodiment 24, wherein the method comprisesthe step of attaching several wood boards and distance strips to thesecond and or first wood board and preferably at least two distancestrips between adjacent wood boards.

26. The method as recited in embodiment 25, wherein the method comprisesthe step of arranging the distance strips between adjacent wood boardsin a straight line.

27. The method as recited in embodiment 26, wherein the straight line isoriented at about 45 degrees to the longitudinal direction of the firstwood board.

28. The method as recited in embodiment 26, wherein the straight line isoriented at about 90 degrees to the longitudinal direction of the firstwood board.

29. The method as recited in any one of the embodiments 24-28, whereinthe method comprises the step of cutting the first and the second woodboards and the distance strips in the length direction several (e.g., atleast two) times with a distance between the cuts which is equal to thethickness of the semi-product.

30. The method as recited in embodiment 29, wherein the method comprisesthe step of cutting the first and the second wood boards and thedistance strips in a direction perpendicular to the length direction.

31. The method as recited in any one of the embodiments 24-30, whereinthe method comprises the steps of:

-   -   forming two grooves in a surface of the first wood board; and    -   attaching one of said two distance strips in each groove.

32. The method as recited in embodiment 31, wherein the method comprisesthe steps of:

-   -   forming two grooves in a surface of the second wood board; and    -   attaching one of said two distance strips in each of said        grooves in the surface of the second wood board.

33. A structural element, such as a beam, comprising a web of wood, theweb comprising a first layer comprising wood lamellas and a second layercomprising wood lamellas,

-   -   wherein the first layer is arranged such that the length        direction of at least some of the wood lamellas is oriented        essentially perpendicular to the length direction of at least        some of the wood lamellas in the second layer.

34. The structural element as recited in embodiment 33, wherein a firstwood lamella in the first layer is fixed to a second wood lamella in thefirst layer by a distance element.

35. The structural element as recited in embodiment 33 or 34, wherein afirst wood lamella in the second layer is fixed to a second wood lamellain the second layer by a distance element.

36. The structural element as recited in embodiment 34 or 35, whereinthe width of the distance element is larger than the width of the firstwood lamella and/or the width of the second wood lamella.

37. The structural element as recited in any one of the embodiments33-36, wherein the first layer is fixed to the second layer, preferablyby gluing at some of the distance elements and/or at a crossing of thefirst and the second layer.

38. The structural element as recited in any one of the embodiments33-37, wherein the structural member is a beam, wherein a first flangeis attached to ends of the wood lamellas in the first and a secondlayer, and a second flange is attached to opposite end of the woodlamellas.

1. Building panel comprising a wood lamella core, a decorative surfacelayer on top of the core and balancing layer under the core, the corecomprises several wood lamellas, which are arranged essentially parallelto each other and with long edge to long edge, and a long edge of afirst wood lamella is arranged with a distance to a long edge of anadjacent second wood lamella, wherein the long edge of the first woodlamella is fixed by a distance element to the long edge of the adjacentsecond wood lamella and at a first edge of the building panel, wherein afirst mechanical locking device is formed at the first edge of thebuilding panel and at least partly in the distance element.
 2. Thebuilding panel as claimed in claim 1, wherein the long edge of the firstwood lamella is fixed by a second distance element to the long edge ofthe adjacent second wood lamella and at a second opposite edge of thebuilding panel, wherein the distance element and the second distanceelement are arranged at a distance.
 3. The building panel as claimed inclaim 2, wherein a part of the distance element is positioned in a firstgroove in the first wood lamella, and a part of the second distanceelement is positioned in a second groove in the first wood lamella. 4.The building panel as claimed in claim 3, wherein another part of thedistance element and the second distance element are positioned in athird and a fourth groove, respectively, in the second wood lamella. 5.The building panel as claimed in claim 2, wherein a second mechanicallocking device is formed at the second opposite edge of the buildingpanel and at least partly in the second distance element.
 6. Thebuilding panel as claimed in claim 1, wherein the distance elementextends to a second opposite edge of the building panel, wherein asecond mechanical locking device is formed at the second opposite edgeof the building panel and at least partly in the distance element. 7.The building panel as claimed in claim 5, wherein the first mechanicallocking device is configured to cooperate with the second mechanicallocking device at an essentially identical building panel for verticaland/or horizontal locking of the building panel and the essentiallyidentical building panel.
 8. The building panel as claimed in claim 5,wherein the second mechanical locking device comprises a locking grooveat the second opposite edge of a groove panel.
 9. The building panel asclaimed in claim 1, wherein the first locking device comprises aprotruding strip with a locking element.
 10. The building panel asclaimed in claim 7, wherein the first locking device comprises aprotruding strip with a locking element and the second locking devicecomprises a locking groove at the second adjacent edge, wherein thelocking element and the locking groove are configured to cooperate forthe locking in the horizontal direction.
 11. The building panel asclaimed in claim 7, wherein one of the first or the second lockingdevice comprises a tongue and the other of the first or the secondlocking device comprises a tongue groove, wherein the tongue and thetongue groove are configured to cooperate for the locking in thevertical direction.
 12. The building panel as claimed in claim 1,wherein the distance element is of a different material or of differentproperties than the wood lamellas.
 13. A semi-product for a structuralelement or for a core for a building panel, the semi product comprisingseveral wood lamellas, which are arranged essentially parallel to eachother and with long edge to long edge, a long edge of a first woodlamella is arranged with a distance to a long edge of an adjacent secondwood lamella, and the long edge of the first wood lamella is fixed by adistance element to the long edge of the adjacent second wood lamella.14. The semi-product according to claim 13, wherein the distanceelements comprises wood fibres and is fixed to the first wood lamellaand the adjacent second wood lamella by an adhesive.
 15. Thesemi-product as claimed in claim 13, wherein the distance between thelong edge of the first wood lamella and the long edge of the adjacentsecond wood lamella in the core for the building panel is in the rangeof about 0.5 mm to about 15 mm.
 16. The semi-product as claimed in claim13, wherein the first or the second wood lamella comprises, in itslength direction, two pieces spaced from each other by a space at shortedges of said pieces.
 17. The semi-product as claimed in claim 13,wherein the distance element is positioned at a short edge of the firstand the second wood lamella.
 18. The semi-product as claimed in claim16, wherein an enforcement element is arranged at the space or at a knotor other weakness of the wood lamella.
 19. The semi-product as claimedin claim 13, wherein an outer long edge of the outermost wood lamella isprovided with distance elements.
 20. The semi-product as claimed inclaim 13, wherein a part of the distance element is positioned in agroove in the first wood lamella.
 21. The semi-product as claimed inclaim 13, wherein another part of the distance element is positioned inanother groove in the second wood lamella.
 22. The semi-product asclaimed in claim 13, wherein a third wood lamella is fixed to secondwood lamella by a second distance element, a fourth wood lamella isfixed to the third wood lamella by a third distance element, wherein thedistance element, the second distance element and the third distanceelement are arranged in a straight line.
 23. The semi-product as claimedin claim 22, wherein the straight line is oriented at about 45 degreesto the longitudinal direction of the first wood lamella.
 24. Method ofproducing a semi-product for a structural element or for a core for abuilding panel, wherein the method comprises the step of: attaching atleast two distance strips by an adhesive to a first wood board;attaching a second wood board to the distance strips by an adhesive; andcutting the first and the second wood boards and the distance strips inthe length direction of the wood boards.
 25. The method as claimed inclaim 24, wherein the method comprises the step of attaching severalwood boards and distance strips to the second and or first wood board.26. The method as claimed in claim 25, wherein the method comprises thestep of arranging the distance strips between adjacent wood boards in astraight line.
 27. The method as claimed in claim 26, wherein thestraight line is oriented at about 45 degrees to the longitudinaldirection of the first wood board.
 28. The method as claimed in claim26, wherein the straight line is oriented at about 90 degrees to thelongitudinal direction of the first wood board.
 29. The method asclaimed in claim 24, wherein the method comprises the step of cuttingthe first and the second wood boards and the distance strips in thelength direction several times with a distance between the cuts which isequal to the thickness of the semi-product.
 30. The method as claimed inclaim 29, wherein the method comprises the step of cutting the first andthe second wood boards and the distance strips in a directionperpendicular to the length direction.
 31. The method as claimed inclaim 24, wherein the method comprises the steps of: forming two groovesin a surface of the first wood board; and attaching one of said twodistance strips in each groove.
 32. The method as claimed in claim 31,wherein the method comprises the steps of: forming two grooves in asurface of the second wood board; and attaching one of said two distancestrips in each of said grooves in the surface of the second wood board.33. A structural element comprising a web of wood, the web comprising afirst layer comprising wood lamellas and a second layer comprising woodlamellas, wherein the first layer is arranged such that the lengthdirection of at least some of the wood lamellas is oriented essentiallyperpendicular to the length direction of at least some of the woodlamellas in the second layer.
 34. The structural element as claimed inclaim 33, wherein a first wood lamella in the first layer is fixed to asecond wood lamella in the first layer by a distance element.
 35. Thestructural element as claimed in claim 33, wherein a first wood lamellain the second layer is fixed to a second wood lamella in the secondlayer by a distance element.
 36. The structural element as claimed inclaim 34, wherein the width of the distance element is larger than thewidth of the first wood lamella and/or the width of the second woodlamella.
 37. The structural element as claimed in claim 33, wherein thefirst layer is fixed to the second layer.
 38. The structural element asclaimed in claim 33, wherein the structural member is a beam, wherein afirst flange is attached to ends of the wood lamellas in the first and asecond layer, and a second flange is attached to opposite end of thewood lamellas.